1. Field of the Invention
The present invention relates to a process for pressure rolling continuous material by feeding it between two rolls, which, if necessary, may be supported by additional rolls. At least one of the rolls is designed as a deflection control roll, and includes a nonrotating beam and a roll shell which is rotatable around the beam.
Between the beam and the roll shell is mounted a first row of supporting elements including at least one operational supporting element which is supplied with a hydraulic medium under controllable pressure via a pressure conduit within the beam. The operational supporting element is movably guided relative to the beam in the compression plane, and while exerting pressure in one direction, the operational support is braced against the roll shell.
A second row of supporting elements including at least one counterpressure element is located on the side of the beam that is opposite to the operational supporting elements. This second row of supporting elements can be supplied, by at least one additional pressure conduit, with a hydraulic medium under controllable pressure. The additional pressure conduit is positioned within the beam, and is independent of the operational supporting elements. The counterpressure element is movably guided relative to the beam within the compression plane, with the pressure exerted by the counterpressure element on the roll shell being in the opposite direction to the direction of support of the operational supporting elements.
Moreover, the present invention also relates to an apparatus for performing the process for pressure rolling continuous material by feeding it between two rolls.
2. Discussion of Background and Material Information
The above-discussed rolls having two rows of supporting elements arranged on opposite sides are known and we disclosed, for instance, in CH 541,088 or U.S. Pat. No. 3,802,044, the disclosures of which are incorporated by reference in their entireties. These rolls may be utilized, for example, for pressing or pressure treatment of various types of continuous materials, including textiles, metal foil, plastics and paper, cardboard or fibrous webs.
The rolls act in the compression plane in concert with at least one additional roll. In this configuration, at least one external roll, e.g., the highest or the lowest roll, is designed as a deflection control roll having a roll shell which moves freely relative to the beam in the direction of the press.
During operation of the rolling apparatus, pressure is exerted on the continuous material moving between the rolls by the force of the operational supporting elements acting within the compression plane. In this process, the beam is flexed to some degree. When the upper roll is involved, the supporting elements, which exert pressure in the opposite direction, can accept the dead weight of the roll shell. For the upper and lower rolls, the supporting elements also serve to open the roller apparatus, which may be a glazing machine as described, for example, in CH 383,087 or in DE 1,113,131 whose disclosures are incorporated by reference in their entireties.
During this process, especially for very rapid openings which take less than one second, the pressure within the pressure conduits leading to the operational supporting elements is turned off abruptly, and the roll shell is raised by the counterpressure elements. However, it frequently happens that the counterpressure elements, at least over part of the length of the roll shell, become detached from the roll shell or that the counterpressure elements cannot follow fast enough. Such a separation of the roll shell, even if very brief, is highly undesirable because the hydrostatic lubricating cushion collapses. Such collapse of the hydrostatic lubricating cushion may cause the supporting elements and the roll shell to be damaged when the supporting elements reestablish contact. This is particularly dangerous when the lubricating fluid, such as water or thermal oil, is not very effective.
Moreover, if the pressure drop for the operational supporting elements and the pressure increase for the counterpressure elements are not precisely synchronized, there is a risk that the strain on the roll shell becomes too great. This is particularly dangerous if, for instance, a valve in a pressure conduit fails. Besides, it is also necessary during the opening process to provide the supporting elements with a large amount of oil under high pressure within a relatively short time. It is particularly critical during running operations to open a connection to an accumulator while, simultaneously, keeping the operational supporting elements from being open.